A comic formula wrapped in lonely sentiments, Robert Siegel's "Big Fan" is an engaging portrait of obsession. Siegel, the former editor of "The Onion," wrote "Big Fan" several years ago while attempting to launch his screenwriting career; the darkly humorous story of a New York Giants aficionado caught the eye of Darren Aronofsky, who hired Siegel to write "The Wrestler." By comparing the two works, it's obvious what Aronofsky saw in Siegel's potential. Even more than "The Wrestler," Siegel's directorial debut focuses on the absurdities of sports culture and reveals the tragedy beneath the surface.

A comic formula wrapped in lonely sentiments, Robert Siegel's "Big Fan" is an engaging portrait of obsession. Siegel, the former editor of "The Onion," wrote "Big Fan" several years ago while attempting to launch his screenwriting career; the darkly humorous story of a New York Giants aficionado caught the eye of Darren Aronofsky, who hired Siegel to write "The Wrestler." By comparing the two works, it's obvious what Aronofsky saw in Siegel's potential. Even more than "The Wrestler," Siegel's directorial debut focuses on the absurdities of sports culture and reveals the tragedy beneath the surface.

Comedian Patton Oswalt plays Paul Aufiero, a Staten Island man-child still living with his nagging mother, wasting away at his deadbeat parking garage job, and hanging out with his equally unmotivated buddy Sal (Kevin Corrigan). While staving off criticism of his lifestyle from his ultra-successful brother Jeff (Gino Cafarelli), Paul focuses on the one thing that makes him genuinely happy: The Giants. Specifically, one Giant really gets him going -- linebacker Quantrell Bishop (Jonathan Hamm). That particular interest sets up an unexpectedly somber twist when Paul and Sal spot the player on a late night party binge and end up following him to a Manhattan club. Cowering in the shadow of his hero, Paul reveals a little too much about his stalker tendencies and winds up with a black eye courtesy of Quantrell himself.

At this point, "Big Fan" becomes less about Paul's sports fixation than the desperation he feels over breaking the illusion of his bond with the team. As the media catches wind of the club scuffle, Paul struggles to maintain a low profile and return to his Giants-loving routine. However, as public pressure mounts, he finds it increasingly difficult to remain in the shadows. Oswalt's performance is a subtle, touching accomplishment that manages to generate sympathy and revulsion at once. To supplement that duality, Siegel creates a perfectly droll atmosphere to match the role. Late at night, Paul makes pre-scripted calls to a local sports station, whispering prose -- so as not to wake his mother in the next room -- to declare his faith in the Giants. Oswalt's expressions of glee during these scenes emphasize Paul's personal satisfaction. You may feel bad for him, but he certainly doesn't feel bad for himself. He's immune to takedowns of his lethargic existence. "Have fun in your box," a parking garage customer scoffs at him. Paul takes the negativity with ease. Until the Quantrell incident, of course.

It's not hard to imagine "Big Fan" as an oversized studio project, perhaps a tired comedy based around the exact same premise, but it sure works a lot better with Siegel's subdued approach. His low-budget, lo-fi aesthetics suit the nature of Paul's existence. The filmmaker had no cooperation from the NFL for his production, so Paul and Sal sit outside Giants Stadium and watch the games on television -- which seems like exactly the sort of thing these broke nobodys would do.

Although the editing could use a little tightening up, the production values in "Big Fan" are impressive. Michael Simmonds' shadowy photography takes the movie into film noir territory, especially as Paul takes a page from the Travis Bickle playbook and decides to venture into his enemy's turf -- a sports bar populated by Philadelphia Eagles fans -- for mysterious reasons. The finale is a genuine crowdpleaser, but a unique one that doesn't sacrifice the legitimacy of Paul's experience. Siegel refuses to condescend to his character's limited world. Instead, he tries to understand it, and succeeds.